Down and cross draft heater including airtight ash pit



Sept. 6, 1949. a. A. LANDRY DOWN AND CROSS DRAFT HEATER, INCLUDING AIRTIGHT ASH PIT Filed Feb. 2, 1949 3 Sheets-Sheet 1 FIGURE I INVENTOR. Bertrand A. Lqndry BY ATTORNEY B. A. LANDR Y DOWN AND CROSS DRAFT HEATER, INCLUDING AIRTIGHT ASH PIT Sept. 6, 1949.

3 Sheets-Sheet 2 Filed Feb. 2, 1949 FIGURE 2 INVENTOR.

Bertrand A. Landry 6 6 M ATTORNEY Sept. 6, 1949. B. A. LANDRY DOWN AND CROSS DRAFT HEATER,

INCLUDING AI-RTIGHT ASH PIT 3 Sheets-Sheet 3 Filed Feb. 2, 1949 FIGURE 4 INVENTOR. Bertrand A. Landry FIGURE '3 ATTORNEY Patented Sept. 6, 1949 UNITED STATES PATENT OFFICE DOWN AND CROSS DRAFT HEATER, INCLUDING AIRTIGHT ASH PIT Bertrand A. Landry, Columbus, Ohio Application February 2, 1949, Serial No. 74,083

12 Claims. 1

This invention relates generally to apparatus for burning solid fuel and more particularly to a down and cross draft heater including an air tight ash pit and wherein substantially smokeless combustion is achieved simultaneously with continuous feed, and the present application is a continuation-in-part of my application, Serial No. 781,544, filed October 23, 1947.

A solid fuel heater of the magazine-feed, crossdraft type has been heretofore devised which is capable of achieving smokeless combustion. This heater comprises, in general, a main chamber divided into an upper fuel space and a lower combustion space, and a cross-feed primary air supply and, a secondary air supply on opposite sides of the combustion space, with outlet means disposed on the same side of the combustion space as the secondary air supply. In practice it has been found that such a heater is satisfactory from the'standpoint that it burns without appreciable smoke, but is unsatisfactory in that it requires poking due to the fact that a suspensory arch or layer of caked or agglomerated fuel is formed in the central portion of the main chamber. The arch or layer is directly attributable to the incomplete devolatilization and/or oxidation of the distillation products of the fresh fuel in the chamber and can be destroyed or eliminated only by periodic poking operations.

One of the principal objects of the invention is to provide a solid fuel smokeless burning heater which is an improvement upon previously designed heaters, including that of the aforementioned application, and is characterized by the fact that poking is eliminated.

Another object of this invention is to provide an apparatus for effecting essentially smokeless combustion of normally smoky fuels, in which poking is eliminated by introducing air into the fuel space in such a manner as to remove and/or oxidize the volatiles from the fuel, as well as to produce an ignition rate that is higher than the rate of burning.

A further object of the invention is to provide a smokeless solid fuel burning heater which -is characterized by essentially smokeless combustion, freedom from the necessity of poking, and freedom from pulling.

Other objects of the invention and the various advantages and characteristics of the present heater will be apparent from the following detailed description when read in conjunction with the accompanying drawings wherein:

Figure 1 is a vertical section through a heater embodying the invention, showing the essential parts thereof,

Figure 2 is a similar section, showing the various air passages or ducts together with the path followed by the fuel charge; and

Figures 3 and 4 are horizontal sections taken,

respectively, on the lines 3-3- and 4-4 of Figure I It is knownthat when a coking coal is heated in the relative absence of air, a hard, continuous structure is formed after devolatilization is complete or nearly complete. 0n the other hand, it has been observed that when a coking coal is heated while air is passing around the individual pieces, enough oxidation of the exuded tarry constituents occurs to prevent agglomeration of the individual pieces, so that the final mass consists essentially of separate or distinct non-packing or non-uniting coke pieces. This latter principle has been applied in the production of the instant heater or apparatus for burning solid fuel, wherein means are provided for preventing caking or agglomeration of the fuel.

In the embodiment shown in. the accompanying drawings, the apparatus comprises an improved heater including an outer casing which is shown as a whole at H) and may be cast or formed from sheet metal, or in any desired manner, and may comprise any suitable number of parts or sections and be of any desired shape. However, the particular casing shown is box-like and has a front wall II and a back wall l2. It also has a pair of side walls spaced from one another, a horizontal bottom wall and a horizontal top wall. The lower portion of the casing I0 is provided with a perforate, horizontally extending grate l4 and this defines with the bottom wall and the lower portions of the front, back and side walls an airtight ash-pit l3. Access to the latteris provided by way of an opening which is formed in the lower portion of the front wall and is normally closed by an imperforate door l5. In the upper portion of the casing is a chute ll through which fresh solid fuel may be loaded into the apparatus. Such chute is normally closed by an imperforate firing door l8.

Depending from the fuel-firing chute I! and extending between and connected to the casing side walls is a wall 20 which divides the central portion of the interior of the easing into a vertical heat-transfer space or outlet duct 2! in the area between the wall 20 and the front wall II and a vertical chamber 22 between the wall 20 and the back wall l2. The upper portion of the chamber 22 is a fuel space or magazine 23 and the lower portion is a combustion space 24 directly over the grate.

The lower portion of wall 20 is in the form of an inverted arch 25 and this is disposed at a substantial distance above the grate M in order to effect communication between the combustion space and the lower end of the outlet duct 2!. A passageway 26 passing transversely through the lower portion of the wall 20 divides the lower portion of said wall 20 into two vertical wall portions 28 and 29. Such passageway is open to .this port 22. As

the atmosphere at both of its ends, thus providing a channel for secondary air which passes into the combustion space 24 at the lower portion of the chamber 22 through a single longitudinal full length slot 20 in the arch portion 25 of the wall 20. As shown in Figures 1 and 2, the slot 30 is downwardly inclined in the direction of the back wall l2, so that a portion of the secondary air flows into the combustion space and mixes with the hereinafter described primary air.

In the back wall tal full width port 22 mary or cross-feed air ber 24. An adjustable cover or damper trols the amount of air that-is admitted shown in the drawings, the port 32 is located at a point above the level of the lower end of the arc'h'2i. communicates with outside atmosphere, and is so angled or positioned that the primary air sweeps or bows substantially horizontally over the grate l4 and through the com- .bustion space 24. Also in the back wall l2, which is inclined inwardly toward its top, and positioned above'the port 22, is a second adjustable cover or damper 25 for controlling the inflow of preoxidizing and ignition air to a vertically extending fullwidth duct 26 the upper end of which opens into the fuel space or magazine 23 through a full'width slot 31. A barrier wall 32' separates l2 of the casing is a horizon- .forthe admission of prito the combustion cham- 33 contheinlets provided bythe port 22 and the duct 36.

The slot 31 is located .at or near the level of the bottom of the firing door it, which is at approximately the same level, but opposite the lower, rear edge of an inclined imperforate roof 38 which is disposed above and defines the upper portion of the fuel space or magazine 23. The roof 38 is spaced beneath the top wall of the casing. The upper end'of the vertical heat-transfer space or outlet duct 2| communicates with an upper horizontally disposed heat-transfer space or outlet duct extension I by way .of passageways 12-42 (see Fig. 4) on either side of the fuel firing chute ii. The outlet duct extension 40 is disposed between the roof 38 and the top wall of the casing. A smoke type collar H is ounted upon the rear portion of the casing top all and communicates with the duct extension 40. A smoke pipe or outlet stack (not shown) may be mounted upon the collar 4| and this may, in turn, be provided with a damper or valve for controlling the draft through the heater.

The vertical wall 20, the arch 25, the wall portions 28 and 29, the portions of the back wall l2, and the front wall H near the combustion space as well as the inner face of the vertical heattransfer portion or outlet duct 2|, are all preferabl lined with refractory or other heat resisting materiahin view of the extremely high temperatures to which they are subjected.

In Figure 2, the separate paths followed by the primary, secondary, and pre-oxidizing and ignition air streams are indicated by arrows. It will be seen that the primary, or cross-feed, air is admitted to the combustion space at a point above the grate and passes across the fuel bed in a direction substantially at right anglesto the direction of the downward movement of the fuel through the vertical chamber 22. The secondary air, is admittedto the combustion space through the transverse continuous slot 30, as shown. This air penetrates into the fuel bed to some extent as indicated in Figure 2. It is'also illustrated how the pre-oxidizing andignition air enters the is forwardly and upwardly inclined andthrough chamber 22 at a point approximately level with the bottom of the firing door and passes downward through the fuel bed toward the entrance to the outlet duct 2|. It will be seen that the three air streams converge at a point near the arch 25 and pass into the outlet duct together. It will be further noted that all three air streams have a planar action, that is, each stream extends substantially the entire width of the heater.

The action of this improved heating apparatus under normal operating conditions will now be described. For purposes of this description, it will be assumed that the fuel being burned is bituminous coal, although it will be understood that the mode of operation would not vary appreciably-for other types of solid fuel. Assuming that the appaartus has'been in operation, fresh fuel is supplied on top of the residual fuel bed in the fuel space or magazine 22 so as to fill the chamber 22. Combustion of the coal in the combustion space 24 is supp rted by the primary or' cross-feed air entering through the port 22, the flow. of such air being induced by natural draft. The rate of burning may be controlled by adjustment of the damper 22 or by control of the draft by means of the damper or valve in the smoke pipe. A part'of the heat that is released by the combustion of the fuel is conducted or radiated upwards to the'fresh fuel in the fuel magazine or space 23, another part is transmitted through the walls surrounding the hearth to the outside and the remainder is carried by the gases to the heat exchange space or outlet duct 2 I. The combustion-supporting, or primary air passes through the fuel bed in a direction which is essentially at right angles to the movement of the fuel bed and towards the wall 20, as shown in Figure 2.

The effect of the heat from the burning bed below on the fresh fuel above is to raise the temperature of the fresh fuel to a temperature sufficiently high that by reason of the combined effects of heat and air the distillation products from the coal will oxidize, with solid fuel residue remaining. The air which passes through the duct 36 enters the top of the chamber through the slot 31 and passes downwardly through the green fuel and the partially burned fuel to the entrance to the outlet duct 2|. While the direction of movement of this air is, in the main, diagonally from the slot 31 to the entrance to the outlet duct 2|, the tendency of flowing air to follow the path of least resistance causes air entering through the slot 21 to pass in contact with substantially all of the green fuel and partially burned fuel in the chamber 22. Such air flowing downwardly through the green fuel serves to oxidize the tarry matter distilled from the fuel, to prevent caking of the fuels, and thus, to permit the ignition plane gradually to approach the top of, the charge with the result that the freshfuel is gradually converted to a non-caking or nonagglomerating fuel.

The secondary air that is admitted through the slot 30 maintains a hot zone near the point ence of sufficient air is assured because the devolatilization described above in gradual and sufficient secondary air may be readily provided; the streams of secondary air and of gases passing under the arch' 25 are copenetrating and thus 'become'intimately mixed; furthermore, the high temperature resulting from the various forms of combustion occurring near the arch are communicated to the arch material which serves as a temperature catalyst for combustion.

Experience in using the apparatus with a horizontal roof has shown that occasionally a mixture of air and volatiles collects in the space above the fuel bed and a "pufling of varying degrees of severity results whenever such mixture becomes ignited. It has been found that this undesirable feature can be effectively eliminated by inclining the roof 38, as shown in the drawings. By inclining the roof the volume of the air space above the fuel bed is reduced, and thus the air-gas mixture which may collect above the fuel bed is limited to an amount too small to cause an explosive or pulling action upon ignition. Such action may also be reduced or curtailed as the result of the normal down flow of pre-oxidizing and ignition air through the main vertical chamber 22. The roof 38 is normally inclined downwardly away from the firing door H! to minimize the amount of gas that can collect above the fuel space but there is no correlation between the direction of inclination of the roof and the slot 31.

It should be especially noted that neither the firing door l8 nor the door on the ash pit ii are provided with any sort of opening, so that there is no oportunity for air to be admitted to the combustion space through these doors when they are closed as they normally are during operation of the heater. The only manner in which air can be admitted to the combustion chamber is in the regular fashion already described for passing the primary, secondary and pre-oxidizing and ignition air streams This eliminates any possibility of air streams passing vertically upwards through the fuel bed as in the previous heater apparatus.

It will be obvious that the apparatus herein described for the burning of bituminous coal is applicable to the combustion of other types of solid fuels, such as anthracite coke, charcoal,

lignite, and wood. The present invention is also applicable to different types of heaters, such as stoves, furnaces, and the like. Other changes in the herein described apparatus may be made without departing from the scope of the present invention as will be apparent to those skilled in the art.

The word heater as used in the specification and the following claims, is meant to include all types of apparatus for burning solid fuel, such as furnaces, stoves, boilers, ranges, etc.

What is claimedis:

1. A down-feed cross-draft heater including a casing forming a combustion space and a fuel magazine in vertical sequence, with the combustion space at the lower portion of the casing, a supporting grate spaced from the bottom of the casing and forming with the bottom of the casing a sealed ash pit below the grate, primary air supply means in one wall of the casin and above the level of the grate, an outlet duct extending substantially, entirely across the opposite wall of the casing and opening adjacent to but above said grate, whereby primary air flowing from the supply means moves substantially transversely across the combustion area to the outlet duct and wholly above the grate, and an air supply duct leading from a point below the top of said first named wall and terminating in a port extending horizontally substantially the entire width of the said first-named wall and and adjacent to said adjacent the top to introduce pro-oxidizing and ignition air into the fuel magazine, said fuel magazine being sealed at its upper end except for the said inlet port and said combustion space having exit gas communication solely at the entrance to said outlet duct adjacent to but ing a sealed ash pit below the grate, primary air supply means in one wall of the casing-and above the level of the grate, an outlet duct extending substantially entirely across the opposite wall of such casing and opening adjacent to but above said grate, whereby primary air flowing from the supply means to the outlet duct moves substantially transversely across the combustion area and wholly above the grate, and an air supply duct leading from a point below the top of said first named wall and terminating in a port extending horizontally substantially the entire width of the said first-named wall and adjacent the top to introduce pro-oxidizing and ignition air into the fuel magazine, said fuel magazine being sealed at its upper end except for the said inlet port and said combustion space having exit as communication solely at the entrance to said outlet duct adjacent to but above the grate, whereby the pre-oxidizing and ignition air moves in a generally diagonal direction from the port at the top of the fuel magazine through the fuel to the outlet duct on the opposite side thereof and adjacent to said grate, means for controlling the supply of primary air, and means for controlling the admission of air to said pre-oxidizing and ignition air supply duct.

3. A down-feed cross-draft heater including a casing forming a combustion space and a fuel magazine in vertical sequence, with the combustion space at the lower portion of the casing, a supporting grate spaced from the bottom of the casing and'forming with the bottom of the casing a sealed ash pit below the grate, primary air supply means'in one wall of the casing and above the levelof the grate, an outlet duct extending substantially entirely across the opposite wall of such casing and" opening adjacent to but above said grate, whereby primary air flowing from the supply means to the outlet duct moves substantially transversely across the combustion area and wholly above the grate, and an air supply duct leading from a point below the top of said first-named wall upwardly and terminating at a port extending horizontally substantially the entire width of the said first-named wall and adjacent the top to introduce pre-oxidizing and ignition air into the fuel magazine, said fuel magazine being sealed at its upper end except for the said inlet port and said combustion space having exit gas communication solely at the entrance to said outlet duct adjacent to but above the grate, whereby the pro-oxidizing and ignition air moves in a generally diagonal direction from the port magazine through the fuel the opposite side thereof grate; a normally closed fuel inlet at the top of the casing, the top of said casto the outlet duct on 7 ing being inclined downwardly from the fuel inletto the "port at the top of the fuel magazine to minimize the space above the fuel in the casing and thereby prevent pulling. r h v 4. A down-feed cross-draft heater including a casing forming a combustion space and a fuel casing forming a combustion space and a fuel magazine in vertical sequence. with the combustion space at the lower portion of the casing, a supporting grate for the fuel spaced from the bottom of the casing and forming with the bottom of the casing a sealed ash pit below the grate,

magazine in vertical sequence, with the combustion space at the lower portion of the casing, a supporting grate spaced from the bottom of the casing and forming with the bottom of the easing a sealed ash pit below the grate, primary air supply means in one wall of the casing and above I the level of the grate, an outlet duct extending substantially entirely across-the opposite wall of such casing and opening adjacent tobut above said grate, whereby primary air flowing from the supply means to the outlet duct moves substantially transversely across the combustion areaand wholly above the grate, and an air supply duct leading from a point below the top of said first-named wall'upwardly and terminating in a port extending horizontally substantially the ento the outlet duction the opposite side thereof and adjacent to said grate, the casing being of less height on the pro-oxidizing and ignition airinlet' side than on the opposite side. I

5. A' down-feed cross-draft heater including a casing forming acombustion space and' a fuel ing of less height on the pre-oxidizing and ignla primary air supply opening in onewall of the casing'and above the level of the grate, a hollow wall structure positioned within the casing in closely spaced substantially parallel relation with the opposite wall of said casing to define with such wall an upwardly extending outlet duct for the products of combustion, said hollow wall being of such length that the entrance to the outlet is adjacent to but above said grate, whereby primary air from the supply means moves substantially transversely across the combustion area to the entrance to the outlet duct and wholly above the grate, means for introducing air to said-combustion area at the lower end of said hollow wall structure adjacent the entrance to the outlet duct, andan air supply duct leading from a point below the top of said first-named wallflto terminate in a port extending horizontally substantiallythe entire width of the said first-named wall and adjacent the top thereof 'to'intro'duce pre-oxidizing and ignition air intoth fuel magazine, saidf fuel magazine being sealed; at its. upper,'endfexcept forthe said inlet port and said combustion space having exit gas communication solely at the en-' trance to said outlet duct adjacent'to but above the grate, whereby the pre-oxidiz ing and ignition airmoves in a generally. diagonal direction from the port; at the top of the fuel magazine through the fuel to the outlet duct on the opposite side thereof and adjacent to said grate, the casing betion air inlet side than: on the opp$ite side to magazine in vertical sequence, with the combus-' tion space at the lower portlon rof the casing, a supportinggrate' for the fuel spaced from the bottom of the casing and formingwiththe bottom of the casing a sealed ash pit below the grate, a primary air supply opening in one wall of the casing andabove thenlevel of the grate, a hollow wall structure positioned within the casing in closely spacedsubstantially parallel relation with the oppositewall of said casing to define with such w'all an upwardly extending outlet duct for the products of combustion, said hollow wall being of such length that the'e'ntrance to the outlet duct opens adjacent to but above said grate, whereby primary air from the'supply means moves substantially transversely across the combustion area to the entrance to the outletduct and wholly above the grate, means for width of the said first-named wall and-adjacent the top thereof to introduce ire-oxidizing and ignition air into the fuel magazine, said fuel magazine being sealed at its upper end except for the said inlet port and. said combustionv space having exit, gas communication solely at the en-' trance .to said outlet duct adjacent to but above the grate, whereby the pre-oxidizing and ignition minimize the space above-the fuel in the: casing and thereby prevent puffing;

'7. A down-feed cross-draft heater casing forming acombustion space and a fuel magazine in vertical sequence, with the combustion space at-the lower portion of the casing, a supporting grate for thefuel spaced from the bottom of the casing and forming with the botintroducing air to said combustion area at the lower endof said hollow wall structure adjacent air moves in agenerally diagonal direction from theport at the top of the fuel magazine through the fuel to the outlet 'duct on the opposite side thereof and adjacent to said grate.

6. A down-feed cross-draft heater including a tom'of the casing a sealed ash pit below the grate, a primary air supply opening in one wall of the casing and above the level of the grate, a hollow wall structure positioned within the casing in closely spaced substantially parallel relation with the opposite wall of said casing to define with such wall an upwardly extending outlet duct for the products of combustion, said hollow wall being of such length that the entrance to the outlet is adjacent to but above said grate, whereby primary air from the supply means moves substantially transversely across the combustion area to the entrance to the outlet duct and wholly above the grate, means for introducing air to said combustion area at the lower end of saidhollow wall structure adjacent the entrance to the outlet duct, and an air supply ductleadingfrom a point belowthe top of saidfirst-named wall upwardly to terminatein a portextending horizontally substantially the entire width of the said first-named wall and adjacent the top to introduce Dre-oxidizing and ignition air into the fuelv magazine, said fuel magazine being sealed at its upper end except for the said inlet port and said combustion space having exit gas communication solely at the entrance-to saidoutlet duct adjacent to but above the grate, whereby thepreoxidizing and ignition air moves in a generally diagonal direction from the port at the top of the including a a fuel magazine through the fuel to the outlet duct on the opposite side thereof and adjacent to said .grate, means for controlling the supply of primary air, and means for controlling the admission of air to said pre-oxidizing and ignition air supply duct.

8. A down-feed cross-draft heater including a casing forming a combustion space and a fuel magazine in vertical sequence, with the combustion space at the lower portion of the casing, a supporting grate spaced from the bottom of the casing and forming with the bottom of the casing a sealed ash pit below the grate/primary air supply means in one wall of the confined space and above the level-of the grate, an outlet duct extending substantially entirely across the opposite wall of the casing and opening adjacent to but above said grate, whereby primary air flowing from the supply means moves substantially transversely across the combustion area to the outlet duct and wholly above the grate, and an air supply duct leading from a point below the top of said first named wall upwardly and terminating in a port extending horizontally substantially the entire width oi the said first-named wall and adjacent thetop to introduce pre-oxidizing and ignition air into the fuel magazine, a dividing wall between said primary air supply means and said air supply duct, said fuel magazine being sealed at its upper end except for the said inlet port and said combustion space having exit gas communication solely at the entrance to said outlet duct adjacent to but above the grate, whereby the pre-oxidizing and ignition air moves in a generally diagonal direction from the port at the top of the fuel magazine through the fuel to the outlet duct on the opposite side thereof and adjacent to said grate.

9. A down-feed cross-draft heater including a casing forming a combustion space and a fuel magazine in vertical sequence, with the combustion space at the lower portion of the casing, a

v supporting grate for the fuel spaced from the bottom of the casing and forming with the bottom of the casing a sealed ash pit below the grate, a primary air supply opening in one wall of the casing and above the level of the grate, a hollow wall structure positioned within the casing in closely spaced substantially parallel relation with the opposite wall of said casing to define with such wall an upwardly extending outlet duct for the products of combustion, said hollow wall being of such length that the entrance to the outlet is adjacent to but above said grate, whereby primary air from the supply means moves substantially transversely across the combustion area to the entrance to the outlet duct and wholly above the grate, means for introducing air to said combustion area at the.lower end of said hollow wall structure adjacent the entrance to the outlet duct, and an air supply duct leading from a point below the top of said first-named wall upwardly to terminate in a port extending horizontally substantially the entire width of the said first-named wall and adjacent the top to introduce predxidizing and ignition air into the fuel magazine, air-dividing wall between said primary air supply means and said supply duct, said fuel magazine being sealed at its upper end except for the said inlet port and said combustion space having exit gas communication solely at the entrance to said outlet duct adjacent to but above the grate, whereby the pre-oxidizing and ignition air moves in a generally diagonal direction from the port at the top of the fuel magazine through the fuel to the outlet duct on the opposite side thereof and adjacent to said grate, means for controlling the supply of primary air, and means for controlling the admission of air to said preoxidizing and ignition air supply duct.

10. A heater adapted to burn solid fuel without appreciable smoke and comprising a box-like casing formed of a first pair of opposed vertical walls, a second pair of opposed vertical walls between the first pair, a top wall and a bottom wall, a perforate grate disposed in the casing directly above the bottom wall and defining with said bottom wall and the lower portions of the vertical walls a normally closed and air tight ash pit a substantially vertical hollow wall structure positloned in the casing in closely spaced and substantially parallel relation with one of the vertical walls of the first pair. extending between and connected to the second pair of vertical walls, defining between said hollow wall and said one vertical wall of the first pair an upwardly extending outlet duct for the products of combustion and between said hollow wall and the other vertical wall of the first pair a vertical chamber consisting of an upper fuel space and a, lower combustion space directly above the grate, said hollow wall having the lower portion thereof terminating above the grate inorder that the combustion space is in communication with the lower end of the outlet duct, means in the upper portion of the casing for sealing the upper end of the fuel space from the upperend of the outlet duct, normally sealed means for introducing solid fuel into the fuel space, horizontally elongated primary air supply means disposed above the grate, associated with, and extending transversely across, said other vertical wall of the first pair, connected to receive outside air as primary air, and having a single horizontal full length opening arranged so that all of the primary air flows Substantially horizontally over the grate, through the fuel in the lower portion of the combustion space and towards the lower end of the outlet duct, and means within the casing and directly above the primary air supply means forming a substantially vertical duct having its lower end open to receive outside air as pre-oxidizing and ignition air and its upper end communicating with the upper portion of the fuel space and arranged so that it introduces the preoxidizing and ignition air into said upper portion of the fuel space for flow downwards past the pieces of fuel in the vertical chamber, the hollow wall structure being connected to receive outside air as secondary air and having in the lower portion thereof a single horizontal full width discharge slot facing inwards and downwards and serving to discharge the secondary air so that it flows part way through the fuel in the lower portion of the combustion space, said up. per portion of the fuel space, when the heater is charged with fuel and in operation and the fuel introducing means is sealed, being completely closed except for the upper end of said vertical .duct and the interstices between the pieces of fuel in said vertical chamber.

11. A heater adapted to burn solid fuel without appreciable smoke and comprising box-like casing formed of a first pair of opposed vertical walls, a second pair of opposed vertical walls between the first pair, a. top wall and a bottom wall, a perforate grate disposed in the casing directly above the bottom wall and defining with said bottom wall and the lower portions of the vertical walls a normally closed and air-tight ash pit, a substantially vertical hollow wall structilre positioned in the casing in closely spaced and substantially parallel relation with one of the vertical walls of the first pair, extending be- .tween and connected to the second pair of ver-.

ticalwallsadefining between said hollow wall and "said one vertical wall of the first pair an upwardly extending outlet duct for the products of bustion space is in communication with the lower combustionand" between-said hollow wall and theother vertical 'wall of the first pair a vertical 7 chamber consisting of an upper fuel space and ;'a-, lower combustion space directly above the grate, said ,liollow wall having the lower portion thereof tenninating above the grate in order that the combustion space is in communication with the, lower end' ofthe outlet duct; means in the 'upperportionof the casing for sealing the upper end ofthefu'el space'from the upper end of the outletduct', normally sealed means for introduc '20 ing -solid fuel into the'fuelspace, horizontally elongated primary air-supply means disposed above the grate, associated. with, and extending transversely-across, said other, vertical wall of the flrst'pai -Qconnectedto receive outside air as primary air 'andhaving an opening arranged so thatalliofathe primary air flows substantially 'horizontallylover' the grate, through the fuel in g "the lower portion'fof the combustion space and I towards-*theflowerrendqoftliegoutiet. duct and means withint thecasing-and directly above the v uppiymeans forming a substantiallyf vertical z.-duct having}its'lower-end open to out-v side airaslpre-oxidizing; and ignition air, and its upper end provided with a horizontal substan-- "tially fullgwidth port] communicating with the j upper portion of the fuel space and facing in- I f-wards and downwards so as to cause the preoxidizing and ignition air to flow in a generally diagonally downward path past the pieces of fuel in the-fuel space and in the direction of the lower portion of the hollow wall, said hollow wall structure being connected to receive outside air as secondary air and having inthe lower portion thereof a downwardly and inwardly facing substantially full width slot for discharging the secondary air so that it flows part way through the fuel in the lower portion of the combustion space, said upper portion of the fuel space when the heater is charged with fuel and in operation and the fuel introducing means is sealed, being completely closed except for the upper end of the vertical duct and the interstices between the pieces of fuel in said vertical chamber.

, 12. A heater adapted to burn solid fuel without appreciable smoke and comprising box-like casingjformedofa first pair of opposed vertical walls, a second pair of opposed vertical walls between the first pair, a top wall and a'bott'om wall, pa perforate grate disposed: in the casing directly above the bottom wall and defining ,with said -"bottom'wall andthe lower portions of the verticalwallsa normally closed andairtight ash pit,

. a3subs'tantially vertical hollowwall structure positioned in the casing in closely spaced and substantially parallel relatifon'{-with oneof the ververtical wallof the first pair anv'upwardly' exend of the outlet duct, means in the upper portion of the casing for sealing the upper end of the fuel space from the upper end of the outlet duct, normally sealed means for introducing solid -fuel into the fuel space, horizontally elongated over the grate, through the fuel in the lower portion of the combustion space and towards the lowerend of the outlet duct, and means within the casing and directly above the primary air supply means forming a substantially vertical duct having its lower end open to outside air as pre-oxidizing and ignition air, and its upper end provided with a horizontal substantially full width port communicating with the upper portion of the fuel space and facing inwards and downwards so as to cause the pre-oxidizingjand ignition air to flow in a generally diagonally downwardpath past the pieces of fuel in the fuel space and in the direction of the lower portion of the hollow wall, said hollow wall structure bej tical walls of the" first pair, extending between fand connected to the second pair of vertical walls, definingmetween said hollow wall and said one ing connected to receive outside air as secondary air and having in the lower portion thereof a downwardly and inwardly facing substantially full width slot for discharging the secondary air so that it flows part way through the fuel in the lower portion of the combustion space, said upper portion of the fuel space when the heater is charged with fuel and in operation and the fuel introducing means is sealed, being completely closed except for the upper end of the vertical duct and the interstices between the pieces of fuel in said vertical chamber, and the top wall of the casing being inclined downwardly from the normally sealed means for introducing fuel into the fuel space and said port to minimize the space above the fuel and thereby prevent puffing.

' BERTRAND A. LANDRY.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 552,911 Knauss Jan. 14, 1896 905,366 Reck Dec. 1, 1908 1,034,799 Hugy Aug. 6, 1912 1,501,847 'Howell July 15, 1924 1,544,582 Howell July 7, 1925 1,561,497 Weir Nov. 17, 1925 2,295,781 Fellows et a1. Sept. 15, 1942 2,403,829 Sanford et al July 9, 1946 2,456,570 Stuckey et al Dec. 14, 1948 FOREIGN PATENTS Number Country Date 50,816 Norway May 9, 1932 585,289

Germany Sept. 30, 1933 LAM-Mei. all. 1: r; z

Certificate of Correction Patent No. 2,481,165

September 6, 1949 BERTRAND A. LANDRY It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 21, for the word bows read flows; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 10th day of January, A. D. 1950.

THOMAS F. MURPHY,

Assistant O'ommissz'oner of Patents. 

